fif ‧ teen /ˌfɪfˈtiːn◂/ BrE AmE number , noun
[ Language: Old English ; Origin: fiftene , from fif 'five' + tien 'ten' ]
1 . the number 15:
a coastal village fifteen miles south of Tourane
They met when she was fifteen (=15 years old) .
2 . [countable] a team of 15 players in ↑ Rugby Union
—fifteenth adjective , pronoun :
in the fifteenth century
her fifteenth birthday
I’m planning to leave on the fifteenth (=the 15th day of the month) .